The Measurement of Elderly Volunteers' Optic Nerve Sheath Diameters by Ocular Ultrasonography

Accuracy of Optic Nerve Sheath Diameter Measurements in Pocket-Sized Ultrasound Devices in a Simulation Model

Introduction

Transorbital sonographic measurement of optic nerve sheath diameter (ONSD) is an emerging non-invasive technique for the identification and monitoring of intracranial hypertension. In recent years, new pocket ultrasound devices have become available, and it is uncertain if they have the resolution to measure such small structures appropriately as compared to their predecessors. In this study, we measure the performance of three ultrasound units on a simulation model to establish their precision and accuracy.

Methods

ONSD was measured by three expert point-of-care sonographers using ultrasound machines three times on each of seven discrete ONS model sizes ranging from 3.5 to 7.9 mm. Two pocket ultrasounds (IVIZ, Sonosite, and Lumify, Philips) and one standard-sized portable ultrasound (M-Turbo, Sonosite) were used. Measurements were analyzed for mean error and variance and tested for significance using blocked covariance matrix regression analyses.

Results

The devices differed in their variances (Lumify: 0.19 mm², M-Turbo: 0.26 mm², IVIZ: 0.34 mm²) and their mean error (Lumify: -0.05 mm, M-Turbo: 0.10 mm, IVIZ: -0.10 mm). The difference in mean error between users is not significant (p = 0.45), but there is a significant difference in mean error between devices (p = 0.02).

Conclusions

Accurate ONSD measurement is possible utilizing pocket-sized ultrasound, and in some cases, may be more accurate than larger portable ultrasound units. While the differences in these devices were statistically significant, all three were highly accurate, with one pocket device (Lumify) outperforming the rest. Further study in human subjects should be conducted prior to using pocket ultrasound devices for in vivo diagnosis of intracranial hypertension.

Optic Nerve Ultrasound Evaluation in Animals and Normal Subjects

In recent years, ultrasonographic measurement of the optic nerve sheath diameter (ONSD) has been widely used to identify the presence of increased intracranial pressure (ICP). Intracranial hypertension is a life-threatening condition that can be caused by various neurological and non-neurological disorders, and it is associated to poor clinical results. Ultrasonography could be used to qualitatively and efficiently detect ICP increases, but to reach this purpose, clear cut-off values are mandatory. The aim of this review is to provide a wide overview of the most important scientific publications on optic nerve ultrasound normal values assessment published in the last 30 years. A total of 42 articles selected from PubMed medical database was included in this review. Our analysis showed that ocular ultrasonography is considered to be a valuable diagnostic tool, especially when intracranial hypertension is suspected, but unfortunately this research provided conflicting results that could be due to the different ultrasound protocols. This is mainly caused by the use of B scan alone, which presents several limitations. The use of B-scan coupled with the standardized A-scan approach could give more accurate, and reliable ultrasound evaluation, assuring higher data objectivity.

Ultrasound measurement of the optic nerve sheath diameter in traumatic brain injury: a narrative review

Background : Raised intracranial pressure (ICP) needs to be investigated in various situations, especially in traumatic brain injury (TBI). Ultra-sonographic (US) measurement of the optic nerve sheath diameter (ONSD) is a promising noninvasive tool for assessing elevated ICP. Objectives : This narrative review aimed to explain the history of and indications forUS measurement of ONSD. We focused on the detection of elevated ICP after TBI and discussed the possible improvements in detection methods. Conclusions : US measurement of ONSD in TBI cases provides a qualitative but no quantitative assessment of ICP. Current studies usually calculate their own optimum cutoff value for detecting raised ICP based on the balance between sensitivity and specificity of the method when compared with invasive methods. There is no universally accepted threshold. We did not find any paper focusing on the prognosis of patients benefiting from it when compared with usual care. Another limitation is the lack of standardization. US measurement of ONSD cannot be used as the sole technique to detect elevated ICP and monitor its evolution, but it can be a useful tool in a multimodal protocol and it might help to determine the prognosis of patients in various situations.

High-resolution MRI assessment of optic nerve sheath diameter in adults: optic nerve sheath variation and a new diagnostic tool for intracranial hypertension

BACKGROUND

Assessment of optic nerve sheath diameter (ONSD) is a non-invasive measure of intracranial pressure (ICP). However, it is not clear whether healthy individuals exhibit ONSD variation or whether factors other than ICP affect the ONSD.

PURPOSE

To investigate whether ONSD was correlated with age, sex, height, weight, eyeball transverse diameter (ETD), or body mass index (BMI), and to develop a new diagnostic model to increase the diagnostic accuracy of intracranial hypertension (IH).

MATERIAL AND METHODS

A total of 145 relatively healthy adults and 40 patients with acute IH who underwent high-resolution magnetic resonance imaging (MRI) were enrolled in this study. Linear regression analyses were used to determine the relationship between ONSD and these variables. If correlations were identified, an index ONSDΔ removing variables effects was calculated. ROC analysis was used to assess the IH predictive value of ONSDΔ in terms of sensitivity and specificity.

RESULTS

In relatively healthy adults, there was a correlation between ONSD and BMI (P = 0.002), which can be presented as an index ONSDΔ. The ONSDΔ model better predicted IH than the ONSD model (P = 0.035), with a sensitivity of 70.00%, a specificity of 71.72%, and an AUC of 0.755.

CONCLUSION

A correlation between ONSD and body mass index (BMI) was found using high-resolution MRI. This result indicates that the effects of BMI should be considered along with the ONSD during ICP monitoring. Meanwhile, the index ONSDΔ was better than the ONSD in predicting IH and could be used to obtain a more precise estimation of ICP.

Relationship between internal carotid artery stenosis grade and optic nerve sheath diameter measured by transorbital ultrasonography

PURPOSE

To assess the consequence of the presence, grade, and asymmetry of carotid artery stenoses on the optic nerve sheath diameter (ONSD) measured by ultrasonography.

METHODS

ONSD was measured with B-mode ultrasonography in 129 patients referred for duplex and color Doppler imaging of the carotid arteries. Internal carotid artery stenosis was graded on the basis of peak systolic flow velocity.

RESULTS

The mean ONSD was 3.04 ± 0.38 mm in the patients without or with <50% internal carotid artery stenosis and 2.46 ± 0.35 mm in those with >70% stenosis. There was an average difference of 0.58 mm between the ONSD of the patients with <50% and the patients with >70% stenosis.

CONCLUSION

ONSD is lower in patients with carotid artery stenosis. Carotid arteries should be investigated, especially in patients with cardiovascular risk factors or diseases, before interpreting ONSD values.

Measuring the Optic Nerve Sheath Diameter with Ultrasound in Acute Middle Cerebral Artery Stroke Patients

BACKGROUND

Measurement of the optic nerve sheath diameter (ONSD) with ultrasound enables non-invasive and indirect assessment of increased intracranial pressure (ICP). Although most of the studies were employed with traumatic brain injury patients, it's increasingly popular in acute ischemic stroke (AIS) studies.

OBJECTIVES

Evaluating whether using ONSD as a follow-up measurement would help monitor the thrombolytic therapy (TT) effectiveness and determine the high-risk patients for malignant middle cerebral artery (MCA) syndrome.

METHODS

This prospective observational study was conducted between August 1, 2019, and February 1, 2020, in a tertiary hospital. Forty-four patients were eligible. We determined the TT moment as the time when the first ocular ultrasound measurement would be made (time 0). Also, we decided on the 24^th h after the treatment as the time to perform the second ocular ultrasound measurement (time 24). The National Institute of Health Stroke Scale (NIHSS), the Glasgow Coma Scale (GCS), and the Alberta Stroke Program Early Computed Tomography (ASPECT) scores were evaluated blindly at the time-0 and the time-24. The cut-off value of ONSD was 0.55 mm.

RESULTS

There was no difference in ONSD results before and after the TT (p = 0.414). But, patients with an equal or higher value than cut-off had an increased risk for complications such as malignant-MCA, bleeding, seizure, etc. (p = 0.05). Malignant-MCA was observed in four patients with higher ONSD values. At the time-24, NIHSS decreased, GCS and ASPECT scores increased. Finally, ONSD was positively correlated with the NIHSS and negatively correlated with the GCS at the time-24.

CONCLUSIONS

Monitoring ONSD values in both the emergency department and the intensive care unit may be useful in the early diagnosis of MCA stroke complications and the follow-up of TT's effectiveness.

The measurement of ultrasonographic optic nerve sheath diameter in patients with hyperglycemia

Background:

Diabetes mellitus is a disease associated with several complications in its acute and chronic stages.

Objective:

The aim of the study was to determine the treatment-associated changes in optic nerve sheath diameter in patients admitted to the emergency department due to one of the acute hyperglycemic complications of diabetes mellitus.

Materials and method:

Diabetic patients with serum glucose levels of 250 mg/dL or higher were included in the study. Healthy volunteers were included in the control group. Optic nerve sheath diameter was measured at 0th hour and at the end of the second hour. Blood samples were collected simultaneously with optic nerve sheath diameter measurements.

Results:

The study included 100 individuals. Group 1 included 50 patients and Group 2 included 50 healthy adults. Optic nerve sheath diameter was 4.5 ± 0.4 mm in Group 1 and 4.4 ± 0.5 mm in Group 2 in 0th hour, and no statistical difference was found between the groups (p = 0.162). In Group 1, optic nerve sheath diameter increased 0.6 ± 0.4 mm after the treatment. Of the patients in Group 1, 22 (44%) patients with diabetic ketoacidosis or hyperosmolar hyperglycemic state were assigned to Group 1A and 28 (56%) patients with isolated hyperglycemia were assigned to Group 1B. There was not a difference between the pre- and post-treatment optic nerve sheath diameter values of the patients in Group 1A and Group 1B. Optic nerve sheath diameter was observed to enlarge after treatment. The difference in optic nerve sheath diameter was 0.6 ± 0.4 mm in Group 1A and 0.5 ± 0.4 mm in Group 1B (p = 0.294).

Conclusion:

Pre-treatment optic nerve sheath diameter values of the patients who were diagnosed with one of the acute hyperglycemic complications of diabetes mellitus are not different from healthy adults. Furthermore, optic nerve sheath diameter values do not change with the severity of the disease. However, optic nerve sheath diameter values change with treatment. For this reason, optic nerve sheath diameter can be used to following the development of brain edema.